Ok, I'm going to give my rating of the Vol 9 and the whole series.

Vol 9
I finished this volume quite disappointed, actually. Given is my first BL series completed, I glad bought them and, different than other mangas, didn't regret buying it. But, even though I have many good things to say about it, the last volumes were, in my opinion, the worst from all of the series. Worst might be a strong word, but I was definetely disappointed.
  For me, until Haruki's and Akihiko's arcs were completely, the series was fine - despite being a complex opinion (I mean, it's up to the reader to decide how to feel about Haruki dating Akihiko after that whole couch incident), they ended up being my favorite characters. And then, we return back to Mafuyu having the same problem he had at the beginning of the series, which for me was a waste, because I thought he was already resolved after dating Ue.
  We spent way too much time with Mafuyu making up his mind and his inner thoughts during the concert, which would be fine, IF we knew more about Yuki.

The series as a whole
It's a good series, with a nice pace for a manga. Haruki is, in particular, my favorite character and I like Akihiko too. 
  I didn't like how Ugetsu's story ended with a lack of resolution (so did he get over Akihiko or not? He just seems depressed) and I don't know what to make of it. Also, his and Mafuyu's friendship could have been more developed :/
  I don't really like Hiiragi because of his personality, but what bothered me was his and Shizu's relationship. Shizu's seems like a walking red flag to date. 
  Lastly, we should have been more exposed to Yuki, because I can't feel much empathy towards Mafuyu's pain. And what makes it worse is the fact that it seemed to be a personal conflict resolved in Vol 2 and 3 and then we return from Vol 5/6 onwards. 

I can’t believe it’s over 🥹. This last volume was filled to the brim with emotions. I was just short of hearing the musical performances and feelings that were being sung. 
All in all, wonderful series. It had a few weak volumes, but the last two entries really brought it back.